Here's another one of those bits I had up on Spearfishing.com. Believe it or not but it did prompt a few first time builds a couple of which were very impressive.
So we might imagine that someone in this position would know exactly what it is they want to build but this isn't always the case. What are the options open to us as builders? They fall into two very basic groups - "Rear handled" and "Mid handled".
• REAR HANDLED - These are the traditional styled spear guns that have the handles at the rear like the European styled gun. This gun can be easily loaded from either the hip or chest. This type is popular gun for entry level to advanced divers and scuba divers.
• MID HANDLED - The mid handled spear guns are designed to give spear guns greater manoeuvrability due to the pivot point being closer to the centre of the gun. This is an advantage to have when tracking game and manoeuvring the gun under ledges, through kelp and around wrecks and pilings. Also, the mechanism placement at the rear enables the spear gun to have the maximum length of rubber pull and a longer shaft for a given distance from the handle to the spear tip. This equates to an increase in power and distance. This gun is usually loaded on the chest. This is popular with advanced divers who want manoeuvrability and power.
Another type of sub classification is how the spear shaft rests on the gun, these are: The "rail", the "Enclosed track" and the "Euro" style
• The rail as the name suggests is a U shaped groove that runs down the length of the barrel.
Its purpose is to support the spear shaft both while it rests on the gun to stop it sagging and also during the spear's acceleration on firing; this helps reduce the oscillation of the shaft as the load is applied.
• The enclosed track is an elaboration of the rail like an upside-down "Ώ" Omega forming almost a tube for the spear to rest in and travel down eliminating all flexing of the shaft which is most useful on the huge guns used by those targeting large pelagic fish.
• The Euro style provides support at the trigger and at the muzzle only. The spear is kept from sagging by having a longer than normal shaft that overhangs the muzzle by about 1/3 of its length which counteracts the natural sag over the centre of the barrel. Also the extra length helps improves the guns accuracy. The spear is propelled in straight line by having the power bands (rubbers) aligned level with the central axis of the spear to prevent pulling the back up or down.
So there are your basic choices, it’s up to you which you will choose when you make your gun.
After deciding which of the above options you are going to include in your gun I believe there are 3 major considerations you should think about next:
• What are you going to be doing with your gun? Will you be shooting small fish at close range? (A small low powered gun) or perhaps large fish at long distance? (A large high powered gun)
• Your choice of trigger. Is it readily available? Can you afford it? and can you buy spear shafts that fit it reasonably locally so that you don’t pay a fortune on shipping? and most importantly, will it do what is required of it safely?
• What are you going to make it from? Wood, metal, plastic, carbon fibre or even a mixture of these. Do you have access to tools that will allow you to do the work? Can you actually buy the material of your choice?
The first of the above points will also have a bearing on the mass of the gun. Why is this important? Put simply it is only important when the power of the gun is such that you are in danger of being hit in the mouth by the butt of the gun because of its recoil (EEK!) Basic physics tells us that as the gun is fired, energy is given to both the spear (forward movement) which is what we want and to the gun (backward movement) recoil! To cut a dull mathematical story short, the more mass in your gun, the less will be the recoil and also the power transfer to the spear will improve by a small amount
Hopefully that gives an illustration of the importance of mass to a gun, now it is a pretty cool thing to consider the balance of your gun in the water at this stage too. The buoyancy is related to the mass of the gun not its weight (trust me they are two entirely separate things). When an object is emerged in water it displaces its own mass not its volume or weight. Now if the volume of the gun is less than the volume of the displaced water the gun will float and vice versa. So we need to choose our materials with a degree of caution if we are to end up with a usable tool.
If we bring the above considerations together we can see that it would be unwise to make a five banded power house of a gun from lightweight carbon fibre because when you fire it you are likely to loose your teeth! Likewise it would be less than ideal to make a low powered gun that is used to track fast moving fish out of wood the volume of the gun will increase its resistance to sideways movement in the water.
The trigger issue is the most asked question of them all and one that can sometimes lead to heated debate. Some people want to make their own triggers, well this I think is fine for low powered guns like the Euro style but for high powered guns take my advice and forget it! You can’t guarantee its reliability and the last thing you want it to do is release when you don’t want it to, think about it! There are a good few manufactures that make trigger mechanisms for sale to guys like us and they are not expensive. There are a couple of ways to approach this, buy a complete Euro gun handle and fit your own barrel, or buy an independent trigger mechanism and make the gun fit it.
So we might imagine that someone in this position would know exactly what it is they want to build but this isn't always the case. What are the options open to us as builders? They fall into two very basic groups - "Rear handled" and "Mid handled".
• REAR HANDLED - These are the traditional styled spear guns that have the handles at the rear like the European styled gun. This gun can be easily loaded from either the hip or chest. This type is popular gun for entry level to advanced divers and scuba divers.
• MID HANDLED - The mid handled spear guns are designed to give spear guns greater manoeuvrability due to the pivot point being closer to the centre of the gun. This is an advantage to have when tracking game and manoeuvring the gun under ledges, through kelp and around wrecks and pilings. Also, the mechanism placement at the rear enables the spear gun to have the maximum length of rubber pull and a longer shaft for a given distance from the handle to the spear tip. This equates to an increase in power and distance. This gun is usually loaded on the chest. This is popular with advanced divers who want manoeuvrability and power.
Another type of sub classification is how the spear shaft rests on the gun, these are: The "rail", the "Enclosed track" and the "Euro" style
• The rail as the name suggests is a U shaped groove that runs down the length of the barrel.
Its purpose is to support the spear shaft both while it rests on the gun to stop it sagging and also during the spear's acceleration on firing; this helps reduce the oscillation of the shaft as the load is applied.
• The enclosed track is an elaboration of the rail like an upside-down "Ώ" Omega forming almost a tube for the spear to rest in and travel down eliminating all flexing of the shaft which is most useful on the huge guns used by those targeting large pelagic fish.
• The Euro style provides support at the trigger and at the muzzle only. The spear is kept from sagging by having a longer than normal shaft that overhangs the muzzle by about 1/3 of its length which counteracts the natural sag over the centre of the barrel. Also the extra length helps improves the guns accuracy. The spear is propelled in straight line by having the power bands (rubbers) aligned level with the central axis of the spear to prevent pulling the back up or down.
So there are your basic choices, it’s up to you which you will choose when you make your gun.
After deciding which of the above options you are going to include in your gun I believe there are 3 major considerations you should think about next:
• What are you going to be doing with your gun? Will you be shooting small fish at close range? (A small low powered gun) or perhaps large fish at long distance? (A large high powered gun)
• Your choice of trigger. Is it readily available? Can you afford it? and can you buy spear shafts that fit it reasonably locally so that you don’t pay a fortune on shipping? and most importantly, will it do what is required of it safely?
• What are you going to make it from? Wood, metal, plastic, carbon fibre or even a mixture of these. Do you have access to tools that will allow you to do the work? Can you actually buy the material of your choice?
The first of the above points will also have a bearing on the mass of the gun. Why is this important? Put simply it is only important when the power of the gun is such that you are in danger of being hit in the mouth by the butt of the gun because of its recoil (EEK!) Basic physics tells us that as the gun is fired, energy is given to both the spear (forward movement) which is what we want and to the gun (backward movement) recoil! To cut a dull mathematical story short, the more mass in your gun, the less will be the recoil and also the power transfer to the spear will improve by a small amount
Hopefully that gives an illustration of the importance of mass to a gun, now it is a pretty cool thing to consider the balance of your gun in the water at this stage too. The buoyancy is related to the mass of the gun not its weight (trust me they are two entirely separate things). When an object is emerged in water it displaces its own mass not its volume or weight. Now if the volume of the gun is less than the volume of the displaced water the gun will float and vice versa. So we need to choose our materials with a degree of caution if we are to end up with a usable tool.
If we bring the above considerations together we can see that it would be unwise to make a five banded power house of a gun from lightweight carbon fibre because when you fire it you are likely to loose your teeth! Likewise it would be less than ideal to make a low powered gun that is used to track fast moving fish out of wood the volume of the gun will increase its resistance to sideways movement in the water.
The trigger issue is the most asked question of them all and one that can sometimes lead to heated debate. Some people want to make their own triggers, well this I think is fine for low powered guns like the Euro style but for high powered guns take my advice and forget it! You can’t guarantee its reliability and the last thing you want it to do is release when you don’t want it to, think about it! There are a good few manufactures that make trigger mechanisms for sale to guys like us and they are not expensive. There are a couple of ways to approach this, buy a complete Euro gun handle and fit your own barrel, or buy an independent trigger mechanism and make the gun fit it.